A blade-mounting adaptor for a power tool has a blade-mounting stud on which the blade is mounted at a first end. The blade is mounted upon the stud in a manner such that it is capable of axial motion along the length of the stud when exertion is applied to the blade. The blade is provided with an adjustable pre-set bias force against the axial motion.
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1. A blade coupler for use with a power tool, comprising a blade mounting stud having means at a first end for connecting the stud to a motor shaft and means at an opposite, second end, for supporting a blade upon the stud in an axially-movable manner; a spring mounted on the stud for exerting a biasing force against the blade in a direction towards the second end; and means mounted to the stud for selectively varying the initial biasing force exerted by the spring against the blade.
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This invention relates to a spring force adapter for coupling a round cutting tool or the like, such as a grinder blade, to a power tool such as an electric grinder.
Blades used in tools such as electric grinders are utilized in a variety of applications where precise control of the tool may be required. Such applications include shaving mortar or concrete adhering to old bricks, tiles, concrete or frames and have the objective of removing such foreign matter from the substrate evenly and completely without damaging the substrate. As the grinder blade is engaged with the surface significant loading of the tool can result. The application of excessive force by the tool operator can result in overloading the tool, resulting in excessive current draw, overheating, excessive wear to tool components, or failure.
Such grinders generate significant amounts of dust and debris during operation. As a result of increasingly strict health and environmental regulations and concerns, the grinders often are provided with a safety cover or shield to contain or restrain the dust and debris, along with a vacuum device to collect the materials. Often the safety cover or shield has a mechanism, such as brushes, to provide a measure of a seal between the cover and the workpiece. The blade must be positioned appropriately with respect to the seal to allow appropriate contact with the workpiece to be made while brush contact is preserved.
The blades utilized in connection with the grinders and similar tools are interchangeable and replaceable. It is thus important that each blade when mounted on the tool is positioned properly with respect to the cover or shield to permit proper blade-workpiece contact to be maintained as blades are exchanged and replaced. As grinding is a force-intensive action, sufficient force must be applied to the tool to maintain appropriate contact between the rotating grinding wheel and the workpiece, but not excessive force that can stress or overload either the tool motor or grinding wheel.
It is accordingly the objective of the present invention to provide a coupling for the mounting of a grinder blade or similar rotating tool that can minimize or eliminate damage to the electrical tool due to repetitive and rapid changes in the load or heavy loads and which accommodates the necessary blade positioning for proper and efficient tool operation.
In accordance with the foregoing and other objectives the present invention is a coupling upon which a grinder blade or other rotating tool element is mounted and which in turn is mounted to the tool drive shaft. The blade is spring biased into an operating position at the end of the coupler shaft. Thus the position of the blade with respect to the tool remains constant when blades are changed. Excessive axial forces applied to the blade, such as by the operator pushing the blade into a workpiece, overcome the spring force applied to the blade, allowing the blade to retract along the coupler, relieving the force on the blade. As the excessive force is removed the blade returns to the original position. The level of spring bias is adjustable.
A fuller understanding of the invention will be achieved upon consideration of the following detailed description of a preferred but nonetheless illustrative embodiment thereof, when considered in conjunction with the annexed drawings, wherein:
With initial reference to
Coiled compression spring 22 is mounted on the blade-mounting stud 18 between opposed inner and outer bowl washers 24 and 26, each of which has a central aperture to allow it to be mounted upon the stud. The aperture wall of the inner bowl washer 24 is circular, sized and threaded to mate with the stud threading, allowing the position of the washer along the length of the stud to be adjusted. The aperture of the outer bowl washer 26 is square, sized to allow the washer to slide freely upon the stud but without being able to rotate with respect to the stud.
The blade-mounting stud 18 is dimensioned to be received by the central circular mounting bore of bowl blade 20, which is of conventional construction. Blade retaining bolt 28 threads into the bore of the distal end of the mounting stud, its head 30 holding the blade upon the mounting stud.
Oftentimes the body of a cup blade 20 is of an unhardened metal construction, and is relatively thin. Particularly when mounted to a square spindle slippage may occur, with resulting wear on the cup wheel body. This can lead to the need for blade replacement before the cutting edge is worn.
Blade-mounting stud 46 is multi-sided, and is shown with a main hexagonal portion having the thread surfaces 16 at the face vertices. An extension portion 48 is of reduced diameter, and may be of generally square cross-section, sized to accommodate the blade-mounting bore 36 and to be accommodated by the central mounting bore 50 of adaptor 38, which is of complementary shape and dimensions. Mounting stud 48 again has internal threading to allow it to be mounted either directly to a power tool arbor (not shown) or to an adaptor puck (also not shown). Inner and outer bowl washers 52, 54 function in the same manner as in the previous embodiment, inner washer being threaded to allow positioning along the stud 46. Outer washer 54, however, may have a circular mounting bore, as a non-slip connection between the blade 32 and the stud 46 is established through the mating of the sides if stud extension 48 and adaptor mounting bore 50. Blade retaining bolt 28 again retains the blade (and affixed adaptor 38) at the end of the stud 48. As in the prior embodiment adjustment of the inner bowl washer 52 varies the spring force applied to the blade, allowing the blade to retract along the stud when excessive axial force is applied to the blade by the user.
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Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Mar 27 2006 | OHATA, SHINJI | NAO ENTERPRISE, INC D B A ALPHA PROFESSIONAL TOOLS | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 017658 | /0613 | |
May 15 2006 | Nao Enterprise, Inc. | (assignment on the face of the patent) | / |
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